HTMLCollection.prototype.forEach = Array.prototype.forEach;
HTMLCollection.prototype.slice = Array.prototype.slice;

initTouchkey = (keepPattern, svgid, formid, formfieldid) => {

    let svg = document.getElementById(svgid);
    let form;
    if (formid !== null) {
        form = document.getElementById(formid);
    }
    let formfield = document.getElementById(formfieldid);

    let currentStroke = null;
    let strokeId = 0;
    let doneMap = {};
    let enteredKey = '';

    let drawLine = (fromX, fromY, toX, toY) => {
        let line = document.createElementNS('http://www.w3.org/2000/svg', 'line');
        let id = 'l-' + (strokeId++);
        let idAttr = document.createAttribute('id');
        let classAttr = document.createAttribute('class');
        let x1attr = document.createAttribute('x1');
        let y1attr = document.createAttribute('y1');
        let x2attr = document.createAttribute('x2');
        let y2attr = document.createAttribute('y2');
        let styleAttr = document.createAttribute('style');
        idAttr.value = id;
        classAttr.value = 'l';
        x1attr.value = fromX;
        y1attr.value = fromY;
        x2attr.value = toX;
        y2attr.value = toY;
        styleAttr.value = 'stroke: grey; stroke-width: 5%; stroke-linecap: round';
        line.setAttributeNode(idAttr);
        line.setAttributeNode(classAttr);
        line.setAttributeNode(x1attr);
        line.setAttributeNode(y1attr);
        line.setAttributeNode(x2attr);
        line.setAttributeNode(y2attr);
        line.setAttributeNode(styleAttr);
        svg.appendChild(line);
        return id;
    };

    let endPath = () => {
        svg.removeChild(svg.getElementById(currentStroke));
        currentStroke = null;
    };

    let clearTouchkey = () => {
        doneMap = {};
        enteredKey = '';
        svg.getElementsByClassName('l').slice().reverse().forEach((line) => {
            svg.removeChild(line);
        });
    };

    svg.onmousedown = (ev) => {
        clearTouchkey();
        let svgrect = svg.getBoundingClientRect();
        let minId = '';
        let minDist = Infinity;
        let minx = 0;
        let miny = 0;
        doneMap = {};
        document.getElementsByClassName('c').forEach((circle) => {
            let x = parseFloat(circle.getAttribute('cx')) / 100.0 * svgrect.width;
            let y = parseFloat(circle.getAttribute('cy')) / 100.0 * svgrect.height;
            let dist = Math.pow(ev.offsetX - x, 2) + Math.pow(ev.offsetY - y, 2);
            if (dist < minDist) {
                minDist = dist;
                minId = circle.id;
                minx = x;
                miny = y;
            }
        });
        currentStroke = drawLine(minx, miny, ev.offsetX, ev.offsetY);
        doneMap[minId] = 1;
        enteredKey += minId;
    };

    svg.onmouseup = (ev) => {
        endPath();
        formfield.value = enteredKey;
        if (keepPattern !== true) {
            clearTouchkey();
        }
        if (formid !== null) {
            form.submit();
        }
    };

    svg.onmousemove = (ev) => {
        if (currentStroke != null) {
            let svgrect = svg.getBoundingClientRect();
            let minId = '';
            let minDist = Infinity;
            let minx = 0;
            let miny = 0;
            document.getElementsByClassName('c').forEach((circle) => {
                let x = parseFloat(circle.getAttribute('cx')) / 100.0 * svgrect.width;
                let y = parseFloat(circle.getAttribute('cy')) / 100.0 * svgrect.height;
                let dist = Math.pow(ev.offsetX - x, 2) + Math.pow(ev.offsetY - y, 2);
                if (dist < minDist) {
                    minDist = dist;
                    minId = circle.id;
                    minx = x;
                    miny = y;
                }
            });
            if (minDist < 2000 && !(minId in doneMap)) {
                let line = svg.getElementById(currentStroke);
                line.setAttribute('x2', minx);
                line.setAttribute('y2', miny);
                currentStroke = drawLine(minx, miny, ev.offsetX, ev.offsetY);
                doneMap[minId] = 1;
                enteredKey += minId;
            }
            let line = svg.getElementById(currentStroke);
            line.setAttribute('x2', ev.offsetX);
            line.setAttribute('y2', ev.offsetY);
        }
    };

};